Drill head assemblies generally used for horizontal earth and rock boring usually include a drill head body carrying a plurality of spaced bits wherein a drive shank is carried within a transverse groove in a base portion of the drill head body and welded therein. If a casing is to be inserted at the same time the hole is drilled a wing cutter assembly positionable upon the drive shank is utilized. Since the drive shank is welded to the drill head body, such may not be removed for substitution of a different size drive shank in the field. Moreover, the utilization of a wing cutter assembly is made more difficult and awkward because of the necessity of accommodating same to a drive shank which is welded in place and which may not be substituted to accommodate other equipment. A drill head assembly having a recess in a pilot bit for receiving an insert carried by a drill head body providing a connection formed by interlocking surfaces is illustrated in U.S. Pat. No. 2,886,292.
It is an important object of this invention to provide a drill head assembly having a drill head body, a wing cutter assembly and a drive shank all of which are secured together against rotation by insertable connecting means having interlocking surfaces and being axially pulled together by a longitudinal assembly screw having a head accommodated within a cylindrical opening in a forward portion of the drill head body and a threaded end secured to the drive shank.
Another important object of the invention is the provision of a drill head assembly having a drive shank which is removable for substitution of a drive shank of a different size to accommodate other equipment of varying sizes.
Another important object of the invention is the provision of a versatile drill head assembly which may be readily assembled or disassembled utilizing a socket and insertable connections having interlocking surfaces such as flats which readily receive the extensive torque incidental to rock drilling.
Another object of the invention is the provision of a drill head assembly wherein the wing cutter assembly or block can be taken out of its insertable connection relationship and a drive shank having a similar insertable connection means directly inserted into the drill head body. It is thus seen that the parts can be removed through disassembling and various parts locked into place to accommodate different sizes of equipment for drilling different size holes. Thus, various component parts can be replaced or adjusted on the job site.